The present invention relates to an apparatus for forming a flattened sample flow for passing a sample (liquid specimen) containing particle components such as blood and urine in a wide, thin, flat flow. The apparatus of the present invention is preferably used in an apparatus for analyzing particle images by emitting a strobe light to the flattened sample flow and taking still images of particle components.
The apparatus for taking images of particle components passed in a flat flow and analyzing particles by image processing is disclosed in Japanese Laid-open Patent Sho. 57-500995 or the U.S. Pat. No. 4,338,024. The flow cell possesses a large aspect ratio passage (ratio of length to width, more than scores of times) in the measuring region, forms a flat sheath flow in the passage, and takes the still images of its sample flat flow by a video camera. The passage dimensions in the imaging region is disclosed as being 100 .mu.m in width and 5000 .mu.m in length (the aspect ratio being 50 times). The sheath flow, meanwhile, refers to a flow having the circumference of a suspension of particles covered with a laminar sheath liquid in order to pass the particles by arranging them in one row precisely in the central part of the liquid flow.
On the other hand, the Japanese Laid-open Utility Model Hei. 3-44626 discloses a nozzle divided into plural nozzle openings along the flattening direction with the front end flattened, and a nozzle having a flat discharge opening for use in the cleanliness measurement of a cleanroom used in the manufacture of semiconductors or the like. Certainly, these nozzles are intended to flatten the sample flow, but sheath flow is not used, and they are merely intended to pass a large volume of liquid specimen. With these nozzles alone, the flat flow having a sufficient flatness as required in the present invention (about 10 .mu.m .times.900 .mu.m) is not realized.
In U.S. Pat. No. 4,988,619, fins are disposed flatly across the flow chamber, and cylindrical rods are disposed across the flow chamber. These are, however, intended to enhance the orientation (aligning the direction) of flat particles in the flow cytometry, and it is not possible, as in the cases above, to realize the flatness required in the present invention (about 10 .mu.m.times.900 .mu.m).
In conventional flow cells disclosed in Japanese Laid-open Patent Sho. 57-500995 and U.S. Pat. No. 4,338,024, the thickness of the passage is about the size of the particles to be analyzed, and the dimensions are also required to be precise. Accordingly, it was difficult to manufacture and was expensive. Also because of the thin thickness, they were easily broken and hard to handle.
In the ordinary flow cytometer, the flow cell with an aspect ratio of the passage of about 1 is used. Using such a flow cell, the above problems are avoided, but flat sample flow is not formed in that state. Besides, in the apparatus disclosed in Japanese Laid-open Utility Model Hei. 3-44626 or U.S. Pat. No. 4,988,619, sufficient flat flow cannot be formed.
In the Flow Cytometry Handbook, Science Forum (1984), pp. 399-400, the force acting on the sample flow is mentioned. FIG. 1 is a diagram reprinted from this publication, showing a plan view of the flow cell part as seen from the flow direction. Comparing the, h, and, v, directions, the force fh in the, h, direction having a larger throttling ratio acts more than the force fv in the, v, direction having a smaller throttling ratio. This is used for arranging the direction of cells in the sample in a specific direction, and it is insufficient for forming a flat sample flow. Meanwhile, supposing the forces acting on the sample flow to be fh, fv, they are expressed as fh:fv= A/a:B/b, with the relation A/a&gt;B/b.